Passenger service units of the aforementioned type are known in the state of the art and widely used in civil aircrafts. Generally these passenger service units comprise a passenger light, a passenger air supply device, oxygen masks, warning lights and the like. In some aircrafts one passenger service unit is provided for each seat of passenger and crew member, in other aircrafts one passenger service unit is provided for a couple of seats. Modern civil aircrafts may transfer a number of passengers ranging from about 50 to several hundred of passengers. Since one aircraft may comprise a high number of passenger service units, maintenance of these service units is very time-consuming. This leads to high maintenance costs, especially since the aircraft is on ground during maintenance.